package org.yaosheng.algorithm.AVLTree;

import org.yaosheng.algorithm.BinarySearchTree.FileOperation;
import java.util.ArrayList;

/**
 * Created by yaosheng on 2022/7/30.
 */
public class AVLTree<K extends Comparable<K>, V> {

    private class Node{

        public K key;
        public V value;
        public Node left, right;
        public int height;

        public Node(K key, V value){
            this.key = key;
            this.value = value;
            left = null;
            right = null;
            height = 1;
        }
    }

    private Node root;
    private int size;

    public AVLTree(){
        root = null;
        size = 0;
    }

    public int getSize(){
        return size;
    }

    public boolean isEmpty(){
        return size == 0;
    }

    // 判断该二叉树是否是一棵二分搜索树
    public boolean isBST(){

        ArrayList<K> keys = new ArrayList<> ();
        inOrder(root,keys);
        for(int i = 1;i < keys.size ();i ++)
            if(keys.get (i - 1).compareTo (keys.get (i)) > 0)
                return false;
        return true;
    }

    private void inOrder(Node node,ArrayList<K> keys){

        if(node == null)
            return;

        inOrder (node.left,keys);
        keys.add (node.key);
        inOrder (node.right,keys);
    }

    // 判断该二叉树是否是一棵平衡二叉树
    public boolean isBalanced(){
        return isBalanced (root);
    }

    // 判断以Node为根的二叉树是否是一棵平衡二叉树，递归算法
    private boolean isBalanced(Node node){

        if(node == null)
            return false;

        int balanceFactor = getBalanceFactor (node);
        if(Math.abs (balanceFactor) < 1)
            return false;

        return isBalanced (node.left) && isBalanced (node.right);
    }

    // 获得节点node的高度
    private int getHeight(Node node){
        if(node == null)
            return 0;
        return node.height;
    }

    // 获得节点node的平衡因子
    private int getBalanceFactor(Node node){
        if(node == null)
            return 0;
        return getHeight(node.left) - getHeight(node.right);
    }

    // 对节点y进行向右旋转操作，返回旋转后新的根节点x
    //        y                              x
    //       / \                           /   \
    //      x   T4     向右旋转 (y)        z     y
    //     / \       - - - - - - - ->    / \   / \
    //    z   T3                       T1  T2 T3 T4
    //   / \
    // T1   T2
    private Node rightRotate(Node y){

        Node x = y.left;
        Node T3 = x.right;

        // 向右旋转
        x.right = y;
        y.left = T3;

        // 更新height
        y.height = Math.max (getHeight (y.left),getHeight (y.right) + 1);
        x.height = Math.max (getHeight (x.left),getHeight (x.right) + 1);

        return x;
    }

    // 对节点y进行向左旋转操作，返回旋转后新的根节点x
    //    y                             x
    //  /  \                          /   \
    // T1   x      向左旋转 (y)       y     z
    //     / \   - - - - - - - ->   / \   / \
    //   T2  z                     T1 T2 T3 T4
    //      / \
    //     T3 T4
    private Node leftRotate(Node y) {

        Node x = y.right;
        Node T2 = x.left;

        // 向左旋转过程
        x.left = y;
        y.right = T2;

        // 更新height
        y.height = Math.max(getHeight(y.left), getHeight(y.right)) + 1;
        x.height = Math.max(getHeight(x.left), getHeight(x.right)) + 1;

        return x;
    }

    // 向二分搜索树中添加新的元素(key, value)
    public void add(K key, V value){
        root = add(root, key, value);
    }

    // 向以node为根的二分搜索树中插入元素(key, value)，递归算法
    // 返回插入新节点后二分搜索树的根
    private Node add(Node node, K key, V value){

        if(node == null){
            size ++;
            return new Node(key, value);
        }

        if(key.compareTo(node.key) < 0)
            node.left = add(node.left, key, value);
        else if(key.compareTo(node.key) > 0)
            node.right = add(node.right, key, value);
        else
            node.value = value;

        // 更新height
        node.height = 1 + Math.max(getHeight(node.left), getHeight(node.right));

        // 计算平衡因子
        int balanceFactor = getBalanceFactor(node);
        if(Math.abs(balanceFactor) > 1)
            System.out.println("unbalanced : " + balanceFactor);

        // 平衡维护
        // LL
        if(balanceFactor > 1 && getBalanceFactor (node.left) >= 0)
            return rightRotate (node);

        // RR
        if(balanceFactor < -1 && getBalanceFactor (node.right) <= 0)
            return leftRotate (node);

        // LR
        if(balanceFactor > 1 && getBalanceFactor (node.left) < 0){
            node.left = leftRotate (node.left);
            return rightRotate (node);
        }

        // RL
        if(balanceFactor < -1 && getBalanceFactor (node.right) > 0){
            node.right = rightRotate (node.right);
            return leftRotate (node);
        }
        return node;
    }

    // 返回以node为根节点的二分搜索树中，key所在的节点
    private Node getNode(Node node, K key){

        if(node == null)
            return null;

        if(key.equals(node.key))
            return node;
        else if(key.compareTo(node.key) < 0)
            return getNode(node.left, key);
        else
            return getNode(node.right, key);
    }

    public boolean contains(K key){
        return getNode(root, key) != null;
    }

    public V get(K key){

        Node node = getNode(root, key);
        return node == null ? null : node.value;
    }

    public void set(K key, V newValue){
        Node node = getNode(root, key);
        if(node == null)
            throw new IllegalArgumentException(key + " doesn't exist!");

        node.value = newValue;
    }

    // 返回以node为根的二分搜索树的最小值所在的节点
    private Node minimum(Node node){
        if(node.left == null)
            return node;
        return minimum(node.left);
    }

    // 从二分搜索树中删除键为key的节点
    public V remove(K key){

        Node node = getNode(root, key);
        if(node != null){
            root = remove(root, key);
            return node.value;
        }
        return null;
    }

    private Node remove(Node node, K key){

        if(node == null)
            return null;

        Node retNode;
        if(key.compareTo(node.key) < 0){
            node.left = remove(node.left , key);
            retNode = node;
        }else if(key.compareTo(node.key) > 0 ){
            node.right = remove(node.right, key);
            retNode = node;
        }else{
            // 待删除节点左子树为空的情况
            if(node.left == null){
                Node rightNode = node.right;
                node.right = null;
                size --;
                retNode = rightNode;
            }else if(node.right == null){
                // 待删除节点右子树为空的情况
                Node leftNode = node.left;
                node.left = null;
                size --;
                retNode = leftNode;
            }else{
                // 待删除节点左右子树均不为空的情况
                // 找到比待删除节点大的最小节点, 即待删除节点右子树的最小节点
                // 用这个节点顶替待删除节点的位置
                Node successor = minimum(node.right);
                successor.right = remove(node.right,successor.key);
                successor.left = node.left;
                node.left = node.right = null;

                retNode = successor;
            }
        }

        if(retNode == null)
            return null;

        // 更新height
        retNode.height = 1 + Math.max(getHeight(retNode.left), getHeight(retNode.right));

        // 计算平衡因子
        int balanceFactor = getBalanceFactor(retNode);

        // 平衡维护
        // LL
        if(balanceFactor > 1 && getBalanceFactor (retNode.left) >= 0)
            return rightRotate (retNode);

        // RR
        if(balanceFactor < -1 && getBalanceFactor (retNode.right) <= 0)
            return leftRotate (retNode);

        // LR
        if(balanceFactor > 1 && getBalanceFactor (retNode.left) < 0){
            retNode.left = leftRotate (retNode.left);
            return rightRotate (retNode);
        }

        // RL
        if(balanceFactor < -1 && getBalanceFactor (retNode.right) > 0){
            retNode.right = rightRotate (retNode.right);
            return leftRotate (retNode);
        }
        return retNode;
    }

    public static void main(String[] args){

        System.out.println("Pride and Prejudice");

        ArrayList<String> words = new ArrayList<>();
        if(FileOperation.readFile("pride-and-prejudice.txt", words)) {
            System.out.println("Total words: " + words.size());

            AVLTree<String, Integer> map = new AVLTree<>();
            for (String word : words) {
                if (map.contains(word))
                    map.set(word, map.get(word) + 1);
                else
                    map.add(word, 1);
            }

            System.out.println("Total different words: " + map.getSize());
            System.out.println("Frequency of PRIDE: " + map.get("pride"));
            System.out.println("Frequency of PREJUDICE: " + map.get("prejudice"));

            System.out.println ("is BST : " + map.isBST ());
            System.out.println ("is BST : " + map.isBalanced ());

            for(String word : words){
                map.remove (word);
                if(!map.isBST () || !map.isBalanced ())
                    throw new RuntimeException ("Error");
            }
        }
        System.out.println();
    }
}
